1. Field of the Invention
The present invention generally relates to exhaust system testing devices and methods and, more particularly, toward methods and devices for testing exhaust gas recirculation systems.
2. Description of Related Art
In low emission automobiles it is conventional to recirculate a portion of the exhaust back to the intake manifold to be mixed with the incoming air and subsequently returned to the combustion chamber. Such exhaust gas recirculation (EGR) systems work well in reducing some emissions by lowering engine""s maximum combustion temperatures.
The prior art has focused on devices for making EGR systems more effective in delivering exhaust gases to the intake manifold, including provision of dedicated valves to control the flow of exhaust gases. Unfortunately, such EGR systems are susceptible to carbon build-up that, over time, reduces their effectiveness. While there exists some theories as to the causes for such carbon build-up, to date there is no effective device for testing different variables to see how they affect the carbon deposition problem.
U.S. Pat. No. 5,693,874 to De La Cruz et al. discloses a test apparatus for determining deposit formation characteristics of fuels. The testing method includes testing engine parts in a heated test chamber where different fuels are sprayed on the test parts to determine deposit characteristics.
U.S. Pat. No. 6,079,251 discloses a system and method for analyzing deposit formation or exhaust particulate content. U.S. Pat. No. 5,492,005 to Homan et al. teaches a related system and method.
Accordingly, there exists a need in the art for a method and system for testing EGR systems to determine the effects of variable conditions on the deposition of carbon. There further exists a need in the art for an EGR system experimental testing and measuring system and method.
The present invention is directed toward a method and system for determining the effects of variable conditions on the deposition of carbon in EGR systems.
In accordance with the present invention, a testing jig is adapted to receive exhaust gas from an engine, and includes a main branch and a plurality of side branches. The plurality of side branches includes at least one test branch and at least one control branch. Each of the plurality of side branches, as well as the main branch, include valves and sensors to permit the flow and conditions in each of the branches to be monitored and controlled.
In further accordance with the invention, the main branch extends generally longitudinally while the side branches are somewhat U-shaped. Each of the side branches is connected to the main branch at a first end and at a second end. Between the connections, the main branch includes a main valve that is used to create a restriction to flow. Similarly, each of the side branches includes a valve near its second end that is used to equalize flow through the side branches.
In accordance with the method of the present invention, the test branch is modified relative to the control branch to introduce one variable. The variable may be temperature, oil, water, fuel additives, oil and engine treatments, alcohol, other combustibles that may be used in place of or in conjunction with gasoline, a flow restriction, a flow enlargement, or any other desired physical parameter. The main branch is connected to the engine exhaust, and the flow rates through the control tube and the main tube are equalized, and the engine is operated at a predetermined rate. The test may be conducted for a predetermined time period or until a predetermined pressure drop is sensed in the control tube. Thereafter, the deposits or coatings in the test branch and the control branch are analyzed and compared to determine the effect of the variables introduced into the test branch.